#include <iostream>
using namespace std;

typedef long long ll;
ll a, b, n, ans, k;

int main()
{
	cin >> a >> b >> n;
	k = 5 * a + 2 * b;
	ans += n / k * 7;
	n %= k;
	if(n <= 5 * a)
	{
		ans += n / a + (n % a != 0);
	}
	else
	{
		n -= 5 * a;
		ans += 6 + (n > b);
	}
	cout << ans;
	return 0;
}
